An Elision is done with an apostrophe if deleting a vowel such as “Ev’ry valley…”
It just occurred to me that you might be referring to Elision‿Slurs for joining syllables from two words under one note. Encore 5 lets you do this by hitting the Command key before the Space bar but does not enter a symbol. You can insert an Elision‿Slur in Encore 5 but it’s a bit funky. I find such a character on a web site, copy it to my clipboard and paste it as needed. Doesn’t work in all fonts and it’s not elegant like the solutions offered in Finale, Sibelius, Dorico and Overture.
Since Elision Slurs already exist in Overture, let’s hope that Don adds this feature to Encore 6. From the Overture 5 User Guide:
“Enter an Elision Slur
To add an elision slur between two syllables type the character ‘^’ between the two syllables. Overture will replace this character with small slur when it displays the lyric on your score.”
(Yes, I checked. This does not work in Encore 5)